Weeds continue to evolve as agriculture places selection pressures on them. Weeds have shifted towards annual species in response to traditional tillage and towards shallow-emerging species with reduced tillage. From the 1960's to 1980s, species shifted when selective herbicides controlled some, but not other species. More recently, changes in growth habit (such as germination time) and herbicide resistance have occurred within species. To date, there are approximately 400 instances of resistance with species and herbicide modes of action groups (http://www.weedscience.com/Graphs/ChronologicalIncrease.aspx). With Monsanto's Roundup Ready systems, resistance in troublesome species such as Amaranthus palmeri, Amaranthus rudus, and Conyza canadensis has required proactive changes to weed control programs. With consultation from the academic community and other manufacturers, Monsanto launched the Roundup Ready PLUS platform which is based on Best Management weed control recommendations that include the use of residual herbicides and additional modes of action with glyphosate. The PLUS platform also provides growers with incentives to use residual and alternative MOA herbicides. Additionally, Monsanto and other companies are developing new trait-based herbicide systems that will allow new modes of action to be used in crops where they were not previously available to improve weed control further and to manage and prevent resistance. Currently, Monsanto is developing soybean and cotton with resistance to dicamba, a well established, broadleaf-controlling herbicide. Monsanto is also working to develop other herbicide traits and herbicides. The entire agricultural industry needs to remain vigilant, continue to develop weed control programs with diverse herbicide modes of action, and to recommend diverse cultural and herbicidal methods. However, growers are successfully adjusting their weed control programs with existing technology, controlling weeds, and maintaining crop yields.

Strategies for sustainable weed management

246th National Meeting (2013)

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